HarperCollins’ William Morrow division will launch Witness, a digital-first imprint for mysteries and thrillers, this October, the company announced Tuesday. Witness is part of HarperCollins’ “Impulse” line of books, which also includes digital-first romance, sci-fi/fantasy and young adult books.

The idea behind digital-first lines is that they let publishers take a chance on unknown or new authors, they allow for a faster publishing process and they let authors release more types and lengths of books throughout the year. In many cases, the books are eventually released in print; HarperCollins says that “to date, more than 60 percent of Impulse titles have a print format, with thousands of printed copies sold for each of those books” (though in many cases this means print-on-demand books that don’t make it into bookstores). Publishers also use digital-first lines in the hopes of attracting self-published authors away from Amazon.

In another move to compete with Amazon, HarperCollins announced that as of August 1, authors who sign with Impulse will receive monthly royalties. “There is a true financial benefit to signing with our Impulse imprints,” said Liate Stehlik, SVP and publisher of William Morrow. Amazon Publishing recently started offering monthly royalty payments to its authors.

The first ten titles from Witness will be released in October, and the company says it’s already acquired over 100 full-length titles for Witness. The imprint will also sell digital editions of Agatha Christie’s short stories, starting with the Hercule Poirot stories, which will be available both as e-singles and as a collection.